1. Field of the Invention
The present invention generally relates to a selectively called wireless receiver capable of receiving any of free statement messages and numeral messages. More specifically, the present invention is directed to such a selectively called wireless receiver capable of effectively storing message data in a message memory.
2. Description of the Related Art
Very recently, various selectively called wireless receivers called as "pocket bells" in Japan are commercially available. In this type of selectively called wireless receiver, the sector system capable of effectively storing messages has been employed as the received message management system.
One typical sector system of the selectively called wireless receiver is disclosed in, for instance, Japanese Laid-open Patent Application No. 60-74736 opened in 1985, and Japanese Laid-open Patent Application No. 2-243027 opened in 1990 as its divisional patent application. In this disclosed sector system, the message memory used to store the received message is theoretically subdivided in such a storage unit called as a "sector". Then, the received messages are sequentially stored in the storage area constituted by a set of these sectors. Then, the messages are deleted, saved, and protected in the unit of this sector.
Specifically, in a selectively called wireless receiver capable of receiving free statement messages, the sector system is employed by a message memory in order to increase the storage efficiency for the received free statement messages.
However, in an actual case, a free statement message containing a KANJI character is not always sent to this type of selectively called wireless receiver, but sometimes a short numeral message is sent thereto.
In an usual case, the sector size of the message memory employed in this type of selectively called wireless receiver is set to be equal to 1/2 to 1/8 of the maximum length of the message which will be received. As a result, in the case that the numeral message is received, since one sector is occupied only by the message constructed of several characters, the use efficiency of the message memory is lowered.
To avoid this drawback, it is conceivable to introduce such a method that the sector size of the message memory is reduced so as to improve the use efficiency of the message memory. However, when one long free statement message is received by this method, since a total number of sectors occupied by one message is increased, cumbersome message management is necessarily required.
On the other hand, disk apparatuses have been widely known as the apparatus with employment of the sector system. For instance, Japanese Laid-open Patent Application No. 1-282778 opened in 1989 (entitled "STORAGE MANAGING SYSTEM OF OPTICAL DISK") discloses such a technique that the sector length of the directory storage region is set to be shorter than the sector length of the data storage region in order to increase the storage efficiency. However, the information stored in the directory storage region is not equal to the data saved in the data file, but is equal to the file name used to identify the data file, the retrieve information required to retrieve the data file, and the sector numbers (sector addresses) of the plural sectors for storing the data files, and the like. As a consequence, this conventional storage managing system could not effectively store the data itself contained in the data file.